Pores of a porous material or a porous structure can be classified into three regimes, namely, micropores (<2 nm), mesopores (2-50 nm), and macropores (>50 nm) depending on a diameter size of a pore. By controlling a pore size, a porous material can be used in various fields as a catalyst, a separation system, a low dielectric material, a hydrogen storage material, photonic crystals, an electrode, and the like. Thus, recently, it has attracted a lot of attention.
Such a porous material or structure may include a metallic oxide, an inorganic material such as a semiconductor, a metal, a polymer or a carbon. In particular, a porous structure including a semiconductive metallic oxide can be used in various ways for self-purification of air and water pollution by means of a photocatalytic reaction and a photoelectrochemical conversion, production of hydrogen for hydrogen fuel cells by means of water decomposition, and the like. In particular, due to surface characteristics, ion conductivity, corrosion resistance, and low cost of a porous carbon structure, various kinds and various forms of carbon materials have currently been used.
Conventionally, a template has been used to manufacture a porous carbon structure, and a colloidal crystalline array based on a coaggregate in which spherical silica or latex polymer nanoparticles are arranged has been used as the template. Further, M41S mesoporous silica arranged is manufactured by using a micelle array of a surfactant molecule as a structure-directing agent for silica polymerization. Although there have been efforts to synthesize regularly arranged porous carbon by a template duplication method using zeolite, a mesoporous material, and a colloidal crystal, pores are not regularly arranged in a structure of such carbon.
Porous carbon structures are different in efficiency depending on their structural characteristics including pore distribution, connectivity, a surface area, and surface characteristics. A surface area and a pore volume need to be adjusted appropriately for a purpose of use of a carbon structure. By way of example, when a carbon structure is used in an electrode of a fuel cell, the carbon structure having a large surface area and a large pore volume is used as a carrier, metallic catalyst particles to be carried have a small size and are uniformly distributed in the carbon carrier, so that an active surface area can be increased and fuel and a reaction product can be easily diffused. Thus, activity can be improved. Meanwhile, if the carbon structure has an extremely small pore size, a specific surface area is highly increased, so that the amount of the catalyst material carried can be increased but it becomes difficult to transfer and diffuse a reactant gas or the like and a polymer electrolyte cannot penetrate into micro pores. Thus, efficiency of the catalyst can be decreased and characteristics of the fuel cell cannot be improved.
However, a method for manufacturing a carbon structure in which pores have interconnectivity and various sizes and a method for efficiently manufacturing a porous carbon structure by easily controlling a pore size and a pore shape of the carbon structure have not been known. In particular, there has not been suggested a method for manufacturing a “spherical” carbon structure including pores having an inverse opal structure by “controlling a pore size and a pore shape” of the carbon structure.
Typically, various methods for synthesizing polymer particles have been well known as methods for manufacturing micrometer-sized particles. By way of example, polystyrene (PS) or polymethylmethacrylate (PMMA) particles can be manufactured to be several micrometer-sized particles by means of a polymerization method known as dispersion polymerization. If the particles have a micrometer size or a smaller size, the particles can be manufactured to be micrometer-sized particles by means of emulsion polymerization. Such micrometer-sized particles have been widely used as a monomer for preparing a colloid crystal. However, there is no alternative method for synthesizing a spherical porous carbon structure including uniform particles of “several micrometer size” as a porous carbon structure.